After learning of their affair, Sickles forced his wife to write a signed confession. The nexd day, Sickles looked out of his home in Lafayette Park and saw Key waiting outside.

Sickles rushed outside shot and killed Key in the park. He immediately admitted his guilt.

Newspapers declared Sickles a hero for saving women from Key, a known lecher.

Sickles’ attorney, Edwin M. Stanton, later President Lincoln’s secretary of war, successfully argued that Sickles had been driven insane by his wife’s infidelity.

Sickles was acquitted, the first time temporary insanity was successfully used in a murder trial.

The colorful congressman later became a Union general during the Civil War and lost his leg to cannon fire at Gettysburg. His leg bones remain on display at the Walter Reed Army Medical Center. The leg even made a cameo appearance during the 2012 movie Lincoln.

— Scott McCabe

Daniel Sickles’ leg, along with a cannonball similar to the one that shattered it at Gettysburg, is on display at the National Museum of Health and Medicine in Silver Spring.